Apparatus for producing a picture



Dec. 19, 1967 w. LIMBERGER 3,359,404

APPARATUS FOR PRODUCING A PICTURE Filed Feb. 11, 1964 3 Sheets-Sheet 1Fig. I

Jnven/or:

WALTER L/MBERGER a 65 AGENT,

Dec. 19, 1967 t w. LIMBERGER 3, 0

APPARATUS FOR PRODUCING A PICTURE Filed Feb. 11, 1964 3 Sheabs-Sheet 2Fig. 3

7n van/or:

WALTER L/MBEPGER- AGENT Dec. 19, 1967 w. LIMBE RGER APPARATUS FORPRODUCING A PICTURE 3 Sheets-Sheet 3 Filed Feb. 11, 1964 Fig. 5

WALTER L/MBERGEP United States Patent APPARATUS FOR PRODUCING A PICTUREWalter Limberger, Hamburg-Poppenbuttel, Germany, as-

signor to Lumoprint Zindler K.G., Hamburg, Germany, a corporation ofGermany Filed Feb. 11, 1964, Ser. No. 344,127 Claims. (Cl. 219-216)ABSTRACT OF THE DISCLOSURE Reproduction apparatus for thediffusion-transfer of an image to a copy-receiving sheet from athermallyactivatable latent-image-carrying reproducing sheet having anemulsion layer containing a heat-activatable substance adopted torelease a diffusion medium, comprising a housing, inlet means and outletmeans in said housing respectively for receiving the reproducing sheetand discharging the reproducing and copy-receiving sheets, meansintermediate the inlet means and the outlet means for providing atransport path for the reproducing sheet, a pair of drums disposed onopposite sides of said transport path and rotatable in engagement withthe reproducing and copy-receiving sheets passing therebetween; springmeans resiliently bearing on at least one of the drums for pressing theminto line engagement, means for setting the minimum gap between thedrums; heating means along the path between the drums and the inletmeans and including a heated surface adapted to heat the emulsion layerupon confronting same for thermally activating the substance to at leastpartially release the medium prior to the passage of the sheets betweenthe drums, and means for passing said copy-receiving sheet and thereproducing sheet concurrently between the drums.

The present invention relates to an apparatus for manufacturing apicture by means of an exposed photographic silver-halide layer inconjunction with a receiving layer, wherein these layers are subjectedin mutual contact to a line pressing, and contain the substancesnecessary for the development and fixing, as well as layer formers andsubstances, or wherein the materials of each layer contain substanceswhich form, when heated, media for triggering off and completingsilver-salt diffusion reproduction transfer, development and fixing.

Hitherto; silver-salt diffusion methods applying heat have been carriedout only in laboratories, for example, by heating the material under aheating plate. It is also known in the art to use photographic-emulsionlayers which, or the carrier of which, form an electric conductorthrough which a heating current is passed in order to heat the materialfrom the inside.

It has already been'proposed to provide roller passes for the heating ofemulsion carriers, wherein the individual rollers may be heated todifferent degrees. It has also been proposed to bias the rollerscarrying out a line pressing of the material so that the rollers areresiliently urged one against the other. In addition, the rollers areguided towards an adjustable minimum gap so as to prevent damage to theemulsion layers during the application of line-pressing pressure.

It is an object of the invention to improve the known methods formanufacturing pictures by means of a transfer of substances betweendifferent layers under heating,

It is a further object of the invention to provide a simply constructedapparatus for a particularly efficient development of photographicmaterial under the application of heat.

It is a further object of the invention to provide an arrangementwherein more than one application of heat is effected in correlationwith the applications of pressure,

3,359,404 Patented Dec. 19, 1967 two materials.

tact pressure to a line The invention is based on the fact that, forexample, in the preferred application using the silver-salt-diffusionmethod, a photographic silver-halide layer on a carrier, for example animpregnated paper substrate, and is processed together with a positivelayer arranged on the same carrier so that the layer is in the samematerial, wherein the substances necessary for effecting the reactionsare present in the material, or else positive and negative layers areprocessed which are always located on an emulsion carrier.

During the processing of two materials heat is preferably applied to thematerial prior to the line pressing and the material may give up largerquantities of a medium for diffusion, such as water.

According to a further preferred embodiment the heat is applied directlyto the emulsion side of a sheet of reproduction material. This offers asubstantial advantage compared with known pressing rollers between whichthe materials are passed with the emulsions in contact, because thesecan apply the heat to the layers only through the carriers. This notonly increases the duration of the heating until the required reactionsoccur, but requires also much more heat to be applied and necessitatesthe use of a more heat-resistant emulsion carrier than with the methodaccording to the invention, in which the emulsion layers are heateddirectly. The application of heat from the emulsion side has alsofurther advantages in the case of certain materials, i.e. where thecarrier has applied thereto in superimposed relationship severaldifferent layers, namely the actual reaction layer and one or morefurther layers with one or more substances for effecting individualreaction between these layers and with the reaction layer. By arrangingthese layers in a suitable manner, the application of heat according tothe invention prior to the line pressing may have a beneficial effect onthe course of the reaction.

According to a special embodiment of the invention, the heat is appliedexclusively prior to the line pressing, that is to say, work is carriedout with a cold pair of press rollers. In conjunction with theabove-described advantages of an application of heat according to theinvention there results a new and unexpected solution in that thesubstances in the individual emulsions or materials are individuallytransformed into their reactive conditions while the layers are thensubjected under conpressing in order to carry out the diffusion.

According to another preferred embodiment, preheating is effected at alower temperature than that of the materials during line pressing. Inthis method, materials are preferably used containing an additive whichgives up stored moisture at higher temperatures than other substancesforming constituents of the materials. Also here, the development and,where required, the fixing is timed conveniently so that, for example,the additives are present in layers containing reactive substanceswhichare transformed into their reactive condition conveniently later thanother reactive substances (for example, during the line pressing), andarranged, for example, in a layer former liberating water, such as waterof crystallization, at the temperatures used for the preheating.

The present invention also comprises an embodiment, in which bothmaterials are heated before the line pressing. Moreover, according to apreferred embodiment, the preheating and the heating prior to the linepressing are effected under simultaneous application of pressure on tothe layers, for example, in the form of a line pressure.

' The apparatus according to the invention has a pair of rollers, atleast one of said rollers being biased in the direction towards theother roller, one of the said rollers being driven directly orindirectly, and wherein there is provided at least one delivery trackleading to the gap between this pair of rollers, with a heating unitlocated in this delivery track. Obviously, at least the parts of theequipment in which heat is applied are equipped with an insulatinghousing, possibly containing vents, while the remaining parts arepreferably force ventilated.

According to a further preferred embodiment, there are provided twodelivery tracks which join upstream of the roller gap, and at least oneheating device in one of the delivery tracks. In a special construction,these two delivery tracks need not be thermally separated one from theother and the heating device is conveniently located between the tracksand supplies heat to both of them. In yet another embodiment, theheating device is divided into two units, each in one of the deliverytracks which are conveniently formed in sections in the shape of a cone.

It follows from the preceding statements that a special embodiment willcomprise heating units located laterally of the delivery track or trackswherein the layers on the material sheets passing through the saiddelivery tracks face these heating units during their passage.

According to a further embodiment of the invention, the pair of rollerscontains a heating device in order to apply heat to the materials duringthe line pressing.

The heating device and/ or devices may preferably have the form of heatradiators; in another preferred embodiment, they comprise each apressure roller so that the heating prior to the line pressing iseffected under the application of pressure.

This pressure roller, which may be heated, may be one roller of a pairof pressure rollers or may collaborate with a guide surface which mayalso be heated and forming part of the delivery track.

Further advantages of the invention will become apparent from thefollowing description, given, by way of example, with reference to theaccompanying drawing, showing diagrammatically embodiments of theinvention, and in which:

vinyl alcohol as layer former. This layer contains also preferablypolyvinyl alcohol in addition to alkali and biand trivalent alcohols,preferably glycerine or glycol.

By way of example, the following composition may be wen:

g Initially a first layer consisting of an emulsion having the followingcomposition:

Distilled water ml 100 On this first layer, after it has dried, a secondlayer is supplied having the following composition:

Polyvinyl alcohol g 10 Distilled water ml... Glycerin ml 15 Sodiumacetate, crystallized g 5.0 Sodium carbonate, sicc. g 2.0

The polyvinyl alcohol had a saponification number of 20:, 15 mg./KOH/ g.and :a degree of hydrolysis of 97.5- 995 and a viscosity of 28-14 cp ina 4% aqueous solution at 20 C.

The negative material was a conventional sheet of material, such as are.commercially available for the silver salt diffusion method. This sheetcontains developing substances and is combined after the exposure of apattern with the receiving layer of the positive material and processedaccording to the description of the invention under application of heatand pressure.

There is also the possibility of arranging the lightsensitive layer ofthe negative material and the receiving layer of the positive materialon one layer carrier. To this end, the composition mentioned above inthe second place FIG. 1 is a cross-sectional side elevation of oneembodi- Examples of the substances which may be processed by means ofthe method of the invention include the silver salt diffusion method. Itis known in this method to add to the reaction layers substances which,when heated beyond their melting point, form the medium necessary forthe diffusion. To this end an alkali-metal-salt melt may be provided,and in particular crystalline sodium 'acetate is provided as thesubstance giving up water.

In principle, salts containing water of crystallization may be provided,which have a low melting point and a water-release point which is nottoo high, so that when the substances are heated to temperatures of theorder of, say, 80 or 90 0, other substances provided for the developmentand fixing may dissolve causing the development and fixing of an exposedphotographic layer in a liquid phase.

An example of the receiving or positive material, having in thisinstance several layers, follows: The receiving material has two layers,one containing a fixing agent and silver seeds (nuclei), and the other ametal-salt melt and alkali. Conveniently, the second layer containspolymay be used as receiving layer with the modification that double theamount of sodium acetate is used with only half the amount of sodiumcarbonate; one gram of sicc. potassium metabisulphate is added. Thereceiving layer contains an irreversible polyvinyl alcohol matrix whichincludes the fixing agents and the developer alkali necessary for thereaction. To this layer substances are added which act as reducingagents and which ensure a high residual moisture (biand trivalentalcohols, such as glycerine and glycol). Preferably, a further additiveis an alkaline metal salt known as melting agent, and known also in itsapplication as softener of polyvinyl alcohol, e.g., sodium acetate.

To this reaction layer a photographic silver halide emulsion is applied,containing in addition to developer substances also further additives,such as dehazing agents, stabilizers and additives capable of formingcompounds with alkali of low solubility.

The apparatus according to the invention has generally a pair of rollers1, 2 for carrying out the line pressing of both layers and is shown moreclearly in FIGURES 1 and 2. The rollers 1, 2 are journaled in two posts3, 4 mounted within a housing 5. This housing 5 contains also theterminal and driving unit 6 for the heating devices disposed in theapparatus, such as, for example, heating coils or radiators, and drivenparts, such as the roller 2 or other rollers provided in modifiedembodiments of the invention. The roller 2 is connected through atransmission 7 with the driving unit 6.

The roller 2 is received rotatably in stub shafts 8, 9 in the posts 3,4. The said stub shaft 9 may be a quill shaft containing the leads 10for a heating element 11 located in the hollow roller 2. The supply lead10 or the connecting unit 6 contains an adjust-ing member 87 (variableresistor) for controlling the current supplied to theheating element.The adjusting element 87 serves also for the switching on and off of theheating element 11.

The roller 1 is mounted by means of stub shafts 12, 13 in the sameposts, but in movable bearing blocks 14, 15 which are each affected by apressure spring 16, 17. These bearing means are guided in oblong slotsof the posts. In order to adjust a gap, the movement of the bearingblocks may be limited .by adjustable means, such as spacer inserts 18,19, located under the bearing blocks 14, 15.

The stub shaft 15 is again formed by a quill shaft, containing thesupply leads for a heating element 21. Adjusting elements 87 (variableresistors) are provided in the connecting and driving unit 6- so thatnot only can the heating elements 11 and 21 be adjusted to varioustemperatures, but also only one heating element in one roller need beswitched on.

A delivery track forms a transport path which leads from an inlet slot23 of the housing to the roller gap. In the embodiment shown, the lowerlimit of this track is formed by an endless conveyor belt 24 supportedby rollers and driven from the unit 6 through a transmission 25. Therollers 88 for this conveyor belt are mounted in the side walls of thehousing or frame, parallel to the plane of the drawing, or in framewalls which are parallel to the posts 3, 4. These walls are not shown indetail. The transmission 25 co-operates with a driving gear 89. Theconveyor belt may be perforated, and a heating device, such as a heatradiator may be mounted under its upper run, as shown at 26. The guidesurface 27 of the guide track, forming the upper limit of the deliverytrack, is associated with a downwardly directed heating device 23, forexample, a radiator. Naturally, an apparatus equipped with only one ofthese heating devices also falls within the scope of the presentinvention. The said guide surface 27 is also mounted in the frame wallsextending parallel to the plane of the drawing.

In addition, a so-called heat lock may be arranged wtihin the zone ofthe inlet opening 23; the heat lock can include a pair of rollers 90affected by a weak contact pressure and driven synchronously to thetransporting member 24 and to the pair of rollers 1, 2, so that heat isprevented from escaping towards the operating side of the appliance anda desirable, weak, preparatory line pressure may be exerted.

In FIG. 1, the rollers of the roller pair 90 are adjustably mounted inthe left frame Wall and biased by means of a spring 91, urging the saidrollers towards each other.

Conveniently, the heat is removed by vents 29. The delivery slot 30 ofthe housing 5 is located downstream of the pair of rollers 1, 2.However, an additional heating station, such as a fiat heating element,may be mounted downstream of the pair of rollers.

In the following description of modified embodiments, parts whichcorrespond to those shown in FIGURES 1 and 2 are marked with the samereference numerals; the features described in conjunction with FIGURES 1and 2 are also referred to although not all details are reproduced inthe subsequent figures.

According to FIG. 3, the pair of rollers 1, 2 is associated with twoguide tracks 31, 32. While the FIG. 1 embodiment shows an arrangementfor one material, carrying both the negative and the positive layers,the FIG. 3 embodiment is adapted for processing two separate anddistinct materials, one carrying the positive and the other the negativelayer.

The guide tracks have adjacent inlets 33, 34 and in spaced relationshiptherefrom a roller pair each with roller 35, 36 and 37, 33, adapted toserve as transporting means and heat bathe in the arrangement comprisinga heating unit 39, or else as preheating arrangement, in which at leastone roller of each set of rollers, namely preferably the adjacentlymounted rollers 35, 37 are equipped with heating elements, for example,as described in conjunction with rollers 1 and 2. The rollers through 38are driven and revolve in the direction indicated by the arrows.

The rollers 36 through 38 are rotatably mounted in the left housingwall. The drive is taken from the transmission as shown in FIG. 1 forthe rollers 90.

The heating device 39 is connected into a circuit 93 with a power source94 and an adjusting element 95. These parts may also be located in theconnecting unit 6.

On their remote sides, the guide tracks 31, 32 are defined by the guidemembers 40 and 96, mounted in walls parallel to the plane of thedrawing. The facing sides are equipped with guide elements 97, 98 whichare permeable to heat radiation and consist, for example, of perforatedplastic, wire mesh, or the like.

Between the guide tracks 31, 32, a heating device, equipped for examplewith heat radiators, may be so located that it is effective upwardly anddownwardly, i.e. affecting both guide tracks 31, 32 so that the layersare heated before they reach the rollers 1, 2.

The apparatus according to FIG. 3 shows also a construction for carryingout a two-stage heating, namely once with the application of pressure bythe rollers 35 through 38 and once without the application of pressureby the heating device 39 prior to the line pressing be tween the rollers1, 2, during which a third application of heat may be effected ifdesired.

Conveniently, the guide tracks are so arranged that the materials arebrought together on the lower guide face 40 of the delivery track 32 andrun from there to the gap between the rollers 1 and 2.

FIG. 3 shows a further configuration according to which a third guidetrack 41 is connected to the pair of rollers 1, 2, terminating in a pairof conveyor rollers 42, 43 in front of the delivery slot of theapparatus and in which a further heating device 44 effects theafter-heating of the superimposed materials after the line pressing.Such an additional heating device may also be provided with all types ofapparatus hereinafter described.

The said heating device 44 is connected in a circuit 9 9 with a powersource and an adjusting member. The pair of conveyor rollers 42, 43 ismounted rotatably in the right housing wall. The guide track 41 isdefined at the bottom by the guide element 100 and at the top by theguide element 101, open at least in part towards the heating element 44and mounted in the side walls of the housing.

FIG. 4 shows two separate guide tracks 45, 46 upstream of the pair ofrollers 1, 2 which run together in front of the roller gap 1, 2 eachequipped with a pair of conveyor and/or heating rollers 47, 48 and 49,50, having the construction described in conjunction with the rollers 35through 38 in FIG. 3. The guide elements 102, 163, 104, 105, definingthe guide tracks 45, 46 are mounted in the side walls parallel to theplane of the drawing. They are permeable to heat radiation at leastwithin the zone of the heating elements, such as, for example, throughperforations, in the manner hereinbefore described. The rollers 47through 50 are driven in the sense indicated by the arrows, as mentionedin FIG. 1 in conjunction with roller 90. The possible heating elementarrangements are indicated at 51, 52, 53, 54, and connected with aterminal and driving unit 6 in the same manner as the elements 11 and21.

A circuit is show at 106, indicating the connecting lead, thearrangement of adjusting elements 107 and a power source 108.

A heating arrangement 55, 56 is located along each guide track on themutually facing sides of these tracks, having for example the form of aheat radiator. However, additional heating arrangements 57, 58 onopposite sides of the guide tracks 45, 46, or only these latterarrangements fall also within the scope of the invention.

Moreover, the invention relates also to an embodiment in which one guidetrack, say 46, is free from heating elements, or has only a singleheating element corresponding to the rollers 49, 50, while the otherguide track, for example track 45, has heating elements 55, 57

and/or a heatable pair of rollers 47, 48. The guide track 45 may also beequipped with only a single heating arrangement 55 or 57, conveniently55. This embodiment makes it possible to preheat only the negative orthe positive in a certain manner, for example, in several stages,possibly underpressure, while .the other sheet of material is appliedwithout preheating (or with another preheating) to the cold or hot linepressing between the rollers 1 and 2.

FIG. 5 shows an embodiment with two delivery tracks 59, 60 upstream ofthe pair of rollers 1, 2, each having only one pair of conveyor orheating rollers 61, 62 and 63, 64. The rollers 61 through 64 are locatedrotatably in the housing walls parallel to the plane of the drawing.These side walls also carry the guide members which define the guidetracks 59, 60 towards the top and bottom and the construction of whichis as described hereinbefore. The rollers are equipped with heatingelements 65 through 68 and revolve in the direction of the arrows. Theguide track 60 shows that the guide tracks need not be equipped withguide elements 109 extending over their entire length, in order todefine the delivery. The guide elements may also be perforated,especially those located inside the housing of the apparatus.

The adjusting elements 69 through 72 for the independent switching oradjustment of the heating elements 65 through 68 are shown withreference to the heating elements 65 through 68.

In FIG. 5, a second contact pressure and conveyor roller pair 73, 74 isprovided downstream of the roller pair 1, 2 and may be heatable anddriven in the same manner as this pair ll, 2, making possible anafter-heating under pressure. The heating elements in the roller 73, 74are shown at 112, 113. The circuit 114, the elements of which may beconnected in the terminal unit 6, comprises a power source 115, andadjusting means 116.

FIG. 6 shows a device with a pair of rollers 1, 2 and with two guidetracks 76, 77 divided centrally by a guide member 75. This guide memberis mounted on the side walls and extends into the inlet slot 23.Downstream thereof, there may be heatable conveyor rollers 78, 79mounted in the side walls, driven in the direction indicated by thearrows and biased by springs 80, 81 towards the guide element 75. Therollers are so guided, for example by means of the mounting described inconjunction with the roller 1 above, that they keep a minimum gaprelative to the guide element 75 which is smaller than the thickness ofthe material supplied thereto.

Above the delivery track 76 there may be mounted and fixed to the framea heating arrangement 82, for example, a source of radiation, while theguide element 8-3, defining the lower side of the delivery track 77 andleading to the gap between the rollers 1, 2 may be equipped with aheatingarrangement 84 having the form of an upwardly radiating radiator.The heating devices 82, 84 are individually operable and adjustable.Also the said heating arrangement 84 is mounted to the side walls of theframe. The drawing shows the circuits between the electrical elements110, 111.

FIG. 6 shows an after-heating arrangement 85, similar in construction tothe after-heating stations in FIGS. 3 and 5, combining, for example, thecharacteristic features of these devices and not described in furtherdetail.

It should also be pointed out that the downstream end of anafter-heating device may be equipped with a separating device 86 ofknown construction, such as with pivoting segments or with a pair ofseparating rollers so that the positive'of the developed and fixedpicture is delivered independently of the negative which remains in theapparatus.

The invention is not limited to the embodiments described hereinbeforeby way of example and comprises particularly also various combinationsof the feature disclosed hereinbefore with reference to variousdrawings.

Having thus fully disclosed my invention, what I claim and desire tosecure by Letters Patent is:

1. A reproduction apparatus for the diffusion-transfer of an image to acopy-receiving sheet from a thermallyactivatable latent-image-carryingreproducing sheet having an emulsion layer containing a heat-activatablesubstance adapted to release a diffusion medium, comprising a housing;inlet means and outlet means in said housing respectively for receivingsaid reproducing sheet and discharging said reproducing andcopy-recieivin g sheets; means intermediate said inlet means and saidoutlet means for providing a transport path for said reproducing sheetfor the reproducing sheet and a transport path for said copy-receivingsheet; a pair of drums disposed on opposite sides of said transport pathand rotatable in engagement with the reproducing and copy-receivingsheets passing therebetween; spring means resiliently bearing on atleast one of said drums for pressing them into line engagement; meansfor setting the minimum gap between said drums; heating means along saidpath for said reproducing sheet between said drums and said inlet meansand including a heated surface adapted to heat said emulsion layer uponconfronting same for thermally activating said substance to at leastpartially release said medium prior to the passage of said sheetsbetween said drums; and means for passing said copy-receiving sheet andsaid reproducing sheet concurrently between said drums.

2. An apparatus as defined in claim 1 wherein said inlet means includesa pair of feed rollers, said apparatus further comprising common drive.means for concur rently displacing said feed rollers and said drums atthe identical peripheral speed, said heating means including a resistiveheating body lying along said surface, and adjustable circuit means forcontrolling the temperature of said surface, said heating means beingdisposed at least in part laterally of said transport path of saidreproducing sheet and transferring heat to said reproducing sheet in anonpressed condition thereof.

3. An apparatus as defined in claim 2 wherein said heating meansincludes a plurality of heated rollers directly ahead of said inletmeans.

4. An apparatus as defined in claim 2 wherein sai means providing saidtransport path of said reproducing sheet includes a plurality of guideelements defining between said inlet means and said drums a pair ofseparate branches merging at said drums for said reproducing sheet andsaid copy-receiving sheet, respectively, said heating means beingincluded in said elements.

5. An apparatus as defined in claim 4 wherein said heating means ispositioned between said branches.

6. An apparatus as defined in claim 2 wherein said heating means isprovided at least in part in said feed rollers.

7. An apparatus as defined in claim 2 wherein said transport path ofsaid reproducing sheet is defined at least in part by a plate extendingbetween said inlet means and said drums, said inlet means having slotsfor delivering said sheets to opposite sides of said plate, said feedrollers advancing the respective sheets along the respective sides ofsaid plate for convergence of said sheets at said drums, saidheating'means including heated members closely spaced from said oppositesides of said plate.

8. An apparatus as defined in claim 1, further comprising feed rollersdownstream of, said drums between sai-d drums and said outlet means, andfurther heating means between said drums and said outlet means.

9. An apparatus as defined in claim 8 wherein said further heating meansis included in said feed rollers.

10. An apparatus as defined in claim 1 wherein said means for settingthe minimum gap between said drums includes a pair of journal blocksrotatably supporting at least one of said drums, guide means in saidhousing slidably receiving said blocks for movement of said one drumtoward the other of said drums, and spacer means interchangeablypositionable in said guide means for retaining said one drum in aselected position relatively 3,142,241 7/1964 Lim ela erger 11877 X tothe other drum. 3,202,072 8/1965 Limberger 9589 References Cited3,249,738 5/1966 Simm et al. 2192l6 UNITED STATES PATENTS 5 RICHARD M.WOOD, Primary Examiner. 2,986,987 6/1961 Limberger 95-89 C. L.ALBRITTON, Assistant Examiner.

1. A REPRODUCTION APPARATUS FOR THE DIFFUSION-TRANSFER OF AN IMAGE TO ACOPY-RECEIVING SHEET FROM A THERMALLYACTIVATABLE LATENT-IMAGE-CARRYINGREPRODUCING SHEET HAVING AN EMULSION LAYER CONTAINING A HEAT-ACTIVATABLESUBSTANCE ADAPTED TO RELEASE A DIFFUSION MEDIUM, COMPRISING A HOUSING;INLET MEANS AND OUTLET MEANS IN SAID HOUSING RESPECTIVELY FOR RECEIVINGSAID REPRODUCING SHEET AND DISCHARGING SAID REPRODUCING ANDCOPY-RECEIVING SHEETS; MEANS INTERMEDIATE SAID INLET MEANS AND SAIDOUTLET MEANS FOR PROVIDING A TRANSPORT PATH FOR SAID REPRODUCING SHEETFOR THE REPRODUCING SHEET AND A TRANSPORT PATH FOR SAID COPY-RECEIVINGSHEET; A PAIR OF DRUMS DISPOSED ON OPPOSITE SIDES OF SAID TRANSPORT PATHAND ROTATABLE IN ENGAGEMENT WITH THE REPRODUCING AND COPY-RECEIVINGSHEETS PASSING THEREBETWEEN; SPRING MEANS RESILIENTLY BEARING ON ATLEAST ONE OF SAID DRUMS FOR PRESSING THEM INTO LINE ENGAGEMENT; MEANSFOR SETTING THE MINIMUM GAP BETWEEN SAID DRUMS; HEATING MEANS ALONG SAIDPATH FOR SAID REPRODUCING SHEET BETWEEN SAID DRUMS AND SAID INLET MEANSAND INCLUDING A HEATED SURFACE ADAPTED TO HEAT SAID EMULSION LAYER UPONCONFRONTING SAME FOR THERMALLY ACTIVATING SAID SUBSTANCE TO AT LEASTPARTIALLY RELEASE SAID MEDIUM PRIOR TO THE PASSAGE OF SAID SHEETSBETWEEN SAID DRUMS; AND MEANS FOR PASSING SAID COPY-RECEIVING SHEET ANDSAID REPRODUCING SHEET CONCURRENTLY BETWEEN SAID DRUMS.